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RPC tuning for CNC, other options?

jpndave

Plastic
Joined
May 23, 2016
After extensive researching here and on the web I decided to just post up a question. We have several machines that we are trying to get under power from single-phase source. 100A 250V (two ~124V legs) single phase source supply both locations.

Location 1
• Bridgeport EZPath SD Lathe
• Bridgeport EZTrak mill
• Additional machine down the road, surface grinder, etc. maybe two running at the same time if all of them is not an option.
Have 20HP idler motor for rotary phase converter

Location 1
• Fanuc Robodrill alpha T21iD
• Additional machine down the road, similar size or a little larger
Have 25HP idler motor for rotary phase converter

The questions are in implementation. As we get ready to power these up my concerns are in the balance voltage, stability and quality of the power for the CNC machines and the overall high voltage already which is already pushing the upper limits and the generated leg will likely go way over the top. My understanding is that at least the EZPath can be fussy with the high voltage if not all of the machines.
Possible solutions,
1. Just balance it out and hope for the best using capacitors (what load do we target for best results as the machines cycle?)
2. Use a transformer on the third leg. I have read several recent posts by JST that this is a better way to go. Transformer on the third leg only or get a triple and do all three legs? Is there a thread out there already detailing the transformer third leg option?
3. I have found a couple of VFD units that are probably high enough to work 22KW-30KW. Costs a bit more but if it saves problems down the road would be worth it. If we choose this option is there any advantage to powering the idler with the VFD (soft start that motor) then pull the machine load center off the idler motor?

Thanks in advance for any help you can offer.

Dave
 

CITIZEN F16

Titanium
Joined
May 2, 2021
After extensive researching here and on the web I decided to just post up a question. We have several machines that we are trying to get under power from single-phase source. 100A 250V (two ~124V legs) single phase source supply both locations.

Location 1
• Bridgeport EZPath SD Lathe
• Bridgeport EZTrak mill
• Additional machine down the road, surface grinder, etc. maybe two running at the same time if all of them is not an option.
Have 20HP idler motor for rotary phase converter

Location 1
• Fanuc Robodrill alpha T21iD
• Additional machine down the road, similar size or a little larger
Have 25HP idler motor for rotary phase converter

The questions are in implementation. As we get ready to power these up my concerns are in the balance voltage, stability and quality of the power for the CNC machines and the overall high voltage already which is already pushing the upper limits and the generated leg will likely go way over the top. My understanding is that at least the EZPath can be fussy with the high voltage if not all of the machines.
Possible solutions,
1. Just balance it out and hope for the best using capacitors (what load do we target for best results as the machines cycle?)
2. Use a transformer on the third leg. I have read several recent posts by JST that this is a better way to go. Transformer on the third leg only or get a triple and do all three legs? Is there a thread out there already detailing the transformer third leg option?
3. I have found a couple of VFD units that are probably high enough to work 22KW-30KW. Costs a bit more but if it saves problems down the road would be worth it. If we choose this option is there any advantage to powering the idler with the VFD (soft start that motor) then pull the machine load center off the idler motor?

Thanks in advance for any help you can offer.

Dave

Go with #1 and make sure to balance it with the most common load range running through it. Not sure of your electrical knowledge. Keep the wild leg out of the control circuit and you should be fine. The machines themselves when running should pull the voltage down. If you have a 3 phase compressor that starts against a heavy load keep it off the converter running the CNCs. A lot of us have single phase service that comes in at 250 or maybe a little more. I was in a garage shop with my first CNCs and incoming was 254.
 

jpndave

Plastic
Joined
May 23, 2016
Go with #1 and make sure to balance it with the most common load range running through it. Not sure of your electrical knowledge. Keep the wild leg out of the control circuit and you should be fine. The machines themselves when running should pull the voltage down. If you have a 3 phase compressor that starts against a heavy load keep it off the converter running the CNCs. A lot of us have single phase service that comes in at 250 or maybe a little more. I was in a garage shop with my first CNCs and incoming was 254.

Thanks for the reply. I am probably over thinking this...

I have a 3 phase compressor but it is on it's own circuit driven by a dedicated VFD. Also a Sweco Polisher, again dedicated VFD. This will be for the CNC machines only. I will keep that in mind on the control circuit. I need to get into the machines and see how that is pulled out.
 








 
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